It is standard practice to reduce adverse vibrational effects by balancing the wheel rim and tire assembly by using a balance machine and clip-on lead weights or lead tape weights. The lead balance weights are placed on the rim flange of the wheel and clamped in place in a proper position, or adhered to the wheel in the case of tape weights, as directed by the balancing machine. In general terms, balance is the uniform distribution of mass about an axis of rotation, where the center of gravity is in the same location as the center of rotation. A balanced tire/wheel assembly is one where mass of the tire/wheel assembly mounted on the vehicle's axle-is uniformly distributed around the axle. There are generally two types of balancing, single plane balancing and dual plane balancing. Single plane balancing uses a single weight plane and only addresses “up-and-down” imbalance. Dual plane balancing uses two weight planes and thus eliminates “up-and-down” and “side-to-side” imbalance.
While lead weight balancing has been generally effective, there are several problems associated with their use. Primarily, the standard wheel weights are manufactured from a lead material that has been identified as having a hazardous influence on the environment. Various national and multinational regulating agencies have passed rules restricting the use of lead balance weights in the future. Balance weights that are not properly secured may fall off during use—resulting in an unbalanced tire. A further disadvantage is that the standard clip on balance weight is difficult to attach to many of the newer wheels which have a reduced wheel flange and are too aesthetically unpleasing to be used on the flanges of fancy alloy wheels. In addition, once the balance weight is in position, regardless of whether a clip-on or tape weight, you can no longer adjust to slight to moderate changes in the proper balance location caused by changing tire/wheel assembly operational characteristics, i.e. tire wear, different speeds, changes in loads which change the loaded radius of the tire, etc.
Attempts to overcome some of these difficulties in truck tires and wheels have resulted in the development of automatic balancing rings comprising a 360 degree annular tube filled with weights in combination with a damping fluid. The tubes are typically attached adjacent the wheel flange. However, these devices tend to cause out of balance problems at lower speeds until the weights are properly positioned. In addition, the balancing rings prevent the attachment of wheel covers or detract from the aesthetics of newer alloy wheels.
The standard wheel balancing systems described above have various disadvantages. It would therefore be an advantage to combine the features of the fixed balance weights in a no-lead configuration in a manner that was able to adjust to operational changes in the tire/wheel assembly without the problems associated with balance rings, in a simple and effective manner.